EIT (Electromagnetically Induced Transparency) is a phenomenon that a resonant laser (usually referred to as a probe laser) is not absorbed by a medium. In other words, the medium is transparent for the probe laser. The transparency is induced by a coupling laser.
Via the very special quantum effect, light is slowed down or even trapped in the medium. Many optical control-related applications may be derived from the special quantum effect, such as optical switches or photonic computers. However, as stated in the document, by Stephen E. Harris, Physics Today, July, 37-42 (1997), and the paper by K. J. Boller, Physical Review Letters, vol. 66, number 20, 2593-2596 (1991), the very special quantum effect can only be realized in a very crucial condition, such as a low-temperature environment and a very intense coupling laser. Further, an arbitrary electromagnetic wave is unable to realize the special quantum effect, and the frequency of the incident electromagnetic wave generating EIT of an atom is limited by the characteristic of the atom. Thus, the special quantum effect is hard to apply to electronic components, and the application thereof is pretty limited.